EP1856452B1 - Method and device for controlling cooking processes in a cooking chamber - Google Patents

Abstract

A control method for an oven comprises the steps of determination of the food product, reading out of a corresponding vector from a memory, whereby the vector is at least two-dimensional and previously empirically determined, with a time value and a scalar value, recording the concentration of a gas characteristic of the cooking product by means of a gas sensor, recording a first point, at which the time curve for the gas concentration has the absolute greatest gradient, storage of the same and the corresponding time, recording a second point, at which the time curve of the gas concentration has a zero gradient and storing the corresponding time, determination of the gradient of the straight line through the first and second points, calculation of the cooking duration by multiplication of the straight line gradient by the scalar value and addition of the time value of the vector.

Description

Field of application and state of the art

The invention relates to a method for controlling cooking processes in a cooking chamber.

It is for example from the EP 1 489 361 A1 known to control a cooking process in a cooking appliance without contact. A food is either manually selected or automatically detected. A gas sensor measures the gas concentration in a cooking chamber, for example an oven, from which a cooking quotient is determined in its time course. By comparing the cooking quotient with a final value of the gas concentration, the cooking process can be controlled and, in particular, terminated when, according to the theoretical specifications in connection with the measured gas concentration, the cooking product is ready.

From the US 4,311,895 It is known to arrange a gas sensor in the upper part of a device which is formed similar to a baking oven. This gas sensor has its own heating coil as active heating. Thus, a concentration of a gas can be detected.

Task and solution

The invention has for its object to provide an alternative method available to control a cooking process in a cooking chamber or cooking appliance and to automate as much as possible, with advantageous detection as simple, accurate and error-free runs.

This object is achieved by a method having the features of claim 1. Advantageous and preferred embodiments of the invention are the subject of the other claims and will be in the following explained in more detail. The wording of the claims is incorporated herein by express reference.

For the process, the food to be cooked is determined, which can be done in various ways, as will be explained in more detail below. With this food a vector is linked, which is read from a memory of an evaluation circuit. This vector is derived from a plurality of vectors stored in the memory, which have been previously determined empirically for this method for a plurality of different items to be cooked and then stored in the memory, for example at the factory. The vector is at least two-dimensional and has at least one time value and at least one scalar value. Then, the concentration of a gas characteristic of the determined food to be cooked is measured by a gas sensor. This gas sensor is advantageously designed or configured specifically for this characteristic gas, for example in that it can be controlled differently for particularly good detection of different gases. Then the time course of the concentration of the characteristic gas is measured. A first point is detected at which the concentration has the largest gradient in terms of magnitude. This extreme value of the time course of the concentration can be pronounced both as a maximum and as a minimum. Both this amount of the largest magnitude gradient and the time at which it is reached are stored. Next, a second point is detected where the concentration of the gas is zero gradient. Here only the time of reaching this second point is stored.

Subsequently, a straight line is mathematically laid through the first and the second point and their slope determined. On the basis of this slope or this line, the further calculation of the entire cooking time can be carried out. This is done by keeping the slope of the line is multiplied by the scalar value of the read vector. Subsequently, the time value of the read-out vector is added to it and thus determines the entire cooking time. Compared to the cooking time already passed, the remaining cooking time can be determined. After reaching either an operator can be made aware of the Garende by appropriate signals. Alternatively, the cooking process can be stopped, in particular by switching off a heater in the oven.

In this way, a large variety of different food items can be used for the at least partially automated process or can be cooked in this way. Although the empirical determination of the different vectors for different food items represents a certain effort. However, it can already be determined at the factory and stored in the memory, which represents a justifiable expense for a large number of identical cooking appliances. The detection of the first and second points is also relatively easy, since these two points are very characteristic. The exemplified two-dimensional vector also allows a relatively simple calculation. By integrating these two points as well as their corresponding times, it is possible to cook different foodstuffs with variations in terms of recipe and preparation largely automated. It is also possible to take account of deviations from nominal specifications.

Another advantage of using the gradient of the gas concentration is that in this way, for example, aging phenomena of a gas sensor and an offset, which is due to the environmental conditions during operation of the gas sensor, can be largely avoided or eliminated. Thus, a relatively accurate detection of the determining points is possible.

The determination of the food to be cooked can basically be done in two different ways. On the one hand, it is possible for an operator to enter the food manually or to make it known to the evaluation circuit. For this purpose, a menu guide can be provided with appropriate input means.

On the other hand, it is possible that with a gas sensor from the beginning resulting Gargut gases are detected and evaluated. As a result, a detection of the food in the cooking chamber can be done, as for example in the DE 103 401 46 A1 is described. Here you can start with a generally valid type of heating, for example to a target temperature of 180 ° C or 200 ° C. On the basis of such a general or standardized heating, the food can be detected or recognized by a gas sensor. Such largely automated detection of the food, of course, has the great advantage that the comfort for an operator is greater. However, under certain circumstances, the construction effort or the effort in the evaluation process is greater. Another possibility for the automatic detection or recognition of the food in the cooking chamber is in the German patent application DE 102005011304.4 to which express reference is made.

Advantageously, the detection of the points or of the first point and of the second point takes place algorithmically by forming differences between values of the gradient of the time profile of the concentration of the characteristic gas. This can be done in discrete time intervals with a fixed duration, for example a few seconds.

Furthermore, it is advantageously possible that the sensor signals are not evaluated from the beginning, since in most cases anyway not expected with a very soon approaching end of the cooking process and the processes so to speak not yet settled are. In particular, it should be waited until the oven temperature has approximately approached the final temperature, that is, for example, has reached at least 70%. Advantageously, an evaluation of the sensor signals only starts when the oven temperature has reached 90% of the final temperature or the selected cooking temperature.

The gas sensors can be designed or specified in different ways. On the other hand, they can be designed so that they only detect the concentration of three-atom or even higher-atom gases in the oven. Thus, a certain pre-selection of gases to be detected is possible, which reduces the effort and can increase the reliability of detection. Furthermore, it is possible that the gas sensors to oxygen, nitrogen and / or carbon dioxide are insensitive or do not detect these gases. Nevertheless, it is also possible that in individual cases, under certain circumstances, depending on the food, also one of these three gases is determined, in particular carbon dioxide.

In addition, the humidity in the cooking chamber or the moisture content of the exhaust air or the air in the oven can be detected. For this purpose, a specially designed humidity sensor can be used. The value of this moisture can be used advantageously both for an automatic detection of the food itself and for a determination of an end time of the cooking process.

Characterized in that the gas concentration is measured only near the final temperature of the cooking chamber, the control of a gas sensor can be simplified. A sensor heating and a necessary temperature control is no longer necessary. Both, however, can be realized in an advantageous embodiment of the invention.

An arrangement of the gas sensor or sensors in an exhaust duct of the cooking chamber, in particular in an oven in Wrasenkanal is considered to be particularly advantageous. In fact, in the exhaust air, the gases which are produced during the cooking process in the cooking chamber can be determined relatively concentrated and at the same time uniformly distributed.

Brief description of the drawing

Fig. 1

eine schematische Darstellung eines Backofens mit Gassensor und Steuerung und

Fig. 2

das Diagramm eines Verlaufs der Gaskonzentration sowie ihres Gradienten.

An embodiment of the invention is shown schematically in the drawings and will be explained in more detail below. In the drawings shows:

Fig. 1

a schematic representation of a oven with gas sensor and control and

Fig. 2

the diagram of a course of the gas concentration and its gradient.

Detailed description of the drawings

In Fig. 1 schematically an oven 11 is shown. In the oven 11, the muffle 13 is surrounded by a correspondingly insulated wall 12. Furthermore, in the muffle 13 an oven heater 15 with Upper heat and lower heat arranged and connected to an oven control 16. On a Abstellgitter 18 in the muffle 13 is a baking pan 20 with a dough mixture 22 as food. It can be seen how gas 24 or a gas mixture from the dough mixture 22 flows out through the heating by means of the oven heating 15. This gas 24 contains various ingredients. On the basis of these ingredients, on the one hand, an automatic identification of the food or dough mixture 22 may already be possible at the beginning of the cooking process. Furthermore, by the gas 24, a recognition or calculation of the entire cooking time is possible, as will be explained in more detail below.

In the upper region of the muffle 13, a schematically illustrated Wrasenauslass 14a is shown, which merges into a Wrasenkanal 14b. This Wrasenkanal 14b leads out of the muffle 13 and the oven 11 also in a known manner. In the vapor channel 14b, a gas sensor 26 is arranged. This is connected to a sensor electronics 28. Of course, it is possible and even advantageous in certain embodiments of the invention to provide more than one gas sensor 26 or a plurality of such gas sensors.

With the one illustrated gas sensor 26 or a plurality of gas sensors, a characteristic gas can be detected, which is located in the gas mixture 24. As has been stated above, the baking oven 11 or the controller 16 already knows at this point in time what the cooking product is or that it is the special dough mixture 22.

Depending on this known dough mixture 22, the associated data or characteristic values are stored in a memory of the controller 16, a specific gas or its concentration K is measured in the exhaust gas, which through the vapor channel 14 b from the oven 11 flows. This concentration K is schematically in Fig. 2 shown over time t. As you can see, it rises slowly, then reaches a peak and then falls off relatively steeply. This climax forms the above-mentioned extreme value. It could also be a minimum to be used as an extreme for the evaluation.

At this gas concentration K, the gradient or the first derivative K 'is determined. This is shown in dashed lines in their time course over time t.

For example, by difference formation or similar mathematical methods, the time t1 is determined at which the gradient K 'has its largest value K'1. This is in the diagram in Fig. 2 located.

Furthermore, it is determined when the gradient K 'becomes zero. This time t2 is also drawn. Then, a straight line g, which is shown in phantom, placed by the two previously determined points or purely mathematically determined the slope of this line. This slope m is given by the equation $$\mathrm{m}\mathrm{=}\mathrm{K\; \text{'}}\mathrm{1}\mathrm{/}\left(\mathrm{t}\mathrm{2}\mathrm{-}\mathrm{t}\mathrm{1}\right)$$

Now, a corresponding, stored vector from a memory of the controller 16 is read to the known food or the dough mixture 22. This vector is two-dimensional and contains a time value t0 and a scalar value S0. It can advantageously be determined empirically and for this type of oven 11 as well as certain groups of cooking products, including the dough mixture 22, are determined at the factory and then stored in the controller 16.

Now the calculation of the total cooking time tG is possible according to the equation $$\mathrm{tG}\mathrm{=}\mathrm{m}\mathrm{*}\mathrm{S}\mathrm{0}\mathrm{+}\mathrm{t}\mathrm{0}$$

After expiration of this entire cooking time tG oven heater 15 is turned off either by the controller 16. Alternatively or additionally, a signal may be given to an operator, preferably acoustically and / or optically.

Thus, it is necessary for the method described herein and inventive method that the type of food to be cooked is known. This can either be over in Fig. 1 not shown, for the expert, however, easily realizable input means by an operator to the oven 11 and the controller 16 are entered. Alternatively, for example via the gas sensor 26 on the basis of the gas 24, a recognition of the food or the dough mixture 22 take place, as in the aforementioned German patent application DE 102005011304.4 is described. On the basis of this, the entire gas mixture with respect to its individual gas constituents is no longer examined, but only the concentration K of a characteristic gas 24 is taken into account and detected by the gas sensor 26.

The above-described mathematical methods, in particular the calculation of the gradient K 'of the gas concentration K as well as the determination of the largest value K'1 of K' and associated time t1 and the zero crossing of K 'at the time t2, are known and easy to perform. In this way, an automatic calculation of the total cooking time tG for this cooking product 22 can take place via linking with correspondingly known vectors stored in the controller 16, which in each case belong to a specific cooking product. Then the cooking process can be ended or an operator be made aware of. Thus, this method is therefore used to determine the end time of the cooking process for a food. The necessary awareness of the food can be achieved either by direct input from an operator or automatic detection.

Claims (9)

1. Method for controlling cooking processes in a cooking chamber (13), preferably a baking oven (11) with the following steps:

   - determination of the food product (22) to be cooked,

   - output of a vector (t0, S0) linked to this food product to be cooked from a memory of an evaluation circuit (16, 28), where the vector has been empirically determined beforehand for the method and is at least two-dimensional with a time value (t0) and a scalar value (S0),

   - detection of the concentration (K) of a gas (24) characteristic for the food product (22) using a gas sensor (26) designed / configured for said gas,

   - detection of a first point (t1) at which the time curve of the concentration (K) of the characteristic gas (24) has the highest-amount gradient (K'1),

   - saving of the amount of the highest-amount gradient (K'1) and of the time (t1) that the first point is reached,

   - detection of a second point (t2) at which the time curve of the concentration (K) of the characteristic gas has the gradient (K') zero,

   - storing of the second point (t2) of reaching the second point,

   - determination of the pitch (m) of a straight line through the first and the second points,

   - calculation of the total cooking duration (tG) for the food product (22) by multiplication of the pitch determined for the straight line with the scalar value of the output vector and by addition with the time value of the output vector.
2. Method according to Claim 1, characterized in that the food product (22) is manually preset by an operator at the control (16), in particular by manual input from a menu.
3. Method according to Claim 1, characterized in that a recognition of the food product (22) in question is achieved by evaluating the food product gases (24) generated with the at least one gas sensor (26), where to do so a generally valid heating method is preferably first used for heating.
4. Method according to one of the preceding claims, characterized in that the first point (t1) and the second point (t2) are determined algorithmically by forming the difference using discrete time intervals.
5. Method according to one of the preceding claims, characterized in that sensor signals are not evaluated until the cooking chamber temperature has reached, starting from an unheated cooking chamber (13), at least 70% of a selected cooking temperature, preferably at least 90%.
6. Method according to one of the preceding claims, characterized in that the concentration of 3-atom or higher-atom gases of the food product (22) in the cooking chamber (13) is detected by the gas sensors (26).
7. Method according to one of the preceding claims, characterized in that the detection of the gas (24) is non-sensitive to oxygen, nitrogen and/or carbon dioxide, or these gases are not detected.
8. Method according to one of the preceding claims, characterized in that the moisture in the cooking chamber (13) is detected.
9. Method according to one of the preceding claims, characterized in that certain food product groups are defined which each have a common guidance gas as the mainly characteristic gas (24) generated during the cooking process.

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